This invention relates to a sluice box apparatus for recovering heavy material, such as gold, from an aggregate.
Placer gold deposits are found in areas where veins and lodes of gold have been exposed and eroded due to such forces as glaciers, water and rock slides. Such deposits are found, for example, in certain areas of the Yukon Territory and the province of British Columbia, Canada.
Several different techniques have been developed over many years for separating placer gold from the surrounding aggregate. Prospectors traditionally use a gold pan in creek beds.
A larger scale placer mining operation requires an apparatus such as a sluice box. This consists of a trough placed on an incline and having riffles on the bottom thereof. The riffles are blocks or laterally extending bars for catching the gold. The riffles are commonly placed on top of matting, such as coco mat or indoor/outdoor carpets, which traps the finer gold particles. In use, a stream of water flows along the sluice and gold bearing aggregate is added to the sluice. The gold particles are trapped by the riffles and matting, while the remaining aggregate and water is discharged at the end of the sluice.
Large gold dredges were used for placer mining in the Yukon from the early to mid twentieth century. These dredges commonly used a large revolving screen, or trommel, where the gold-bearing aggregate was washed. The finer gravel passing through the revolving screen was discharged onto a table with a plurality of curved veins for distributing the gravel to a plurality of sluices.
A similar arrangement is seen in U.S. Pat. No. 1,041,486 to King et al. This patent discloses a gold saving table which includes a hopper for receiving material passing through the foraminous wall of a screen, for example a rotary screen. The material from the distributing hopper is discharged onto a gold saving table having a series of channels formed thereon by upwardly extending veins. The channels extend laterally and curve forwardly in a U-shaped arrangement. There are perforated plates at the ends of the channels through which finer particles pass. An auxiliary gold saving table is provided to separate lighter particles.
Canadian Pat. No. 1,074,263 to Ross discloses a similar arrangement employing a distribution table and a separate fine recovery section. The distribution table has a floor transversely downwardly inclined and longitudinally upwardly inclined to slow the fine flurry stream. While the Ross device employs a fixed central recovery channel for coarse material and fixed recovery channels on each side thereof for fine materials, the patent does discuss the possibility that the slope of the fine and coarse recovery channels could be made independently adjustable.
Because the price of gold has increased dramatically in recent years, it has become increasingly important to improve the recovery of gold from such placer mining devices. The devices used in early years were relatively inefficient and a considerable amount of gold, particularly fine material and gold flour, was discharged from the sluice boxes or other devices. For example, in the Ross device found in Canadian Pat. No. 1,074,263, a superfine recovery section has been added to the lower portion of the fine recovery channels to attempt to recover fine material not recovered by the upper portion of the device. However, the need for an inherently more efficient placer mining device remained.